In a patent document 1, there is described a technique in which in an exhaust gas purification apparatus for an internal combustion engine which is provided with a selective reduction type catalyst disposed in an exhaust passage of the internal combustion engine, and an addition valve adapted to add an aqueous urea solution to an exhaust gas before flowing into the selective reduction type catalyst, provision is made for a mixing device (mixer) which is arranged in the exhaust passage eat a location upstream of the selective reduction type catalyst and downstream of the addition valve for promoting the exhaust gas and urea water to mix with each other.
In a patent document 2, there is described a technique in which in an exhaust gas purification apparatus for an internal combustion engine which is provided with a selective reduction type catalyst disposed in an exhaust passage of the internal combustion engine, and an addition valve adapted to add an aqueous urea solution to an exhaust gas before flowing into the selective reduction type catalyst, provision is made for a fin which is arranged in the exhaust passage at a location upstream of the addition valve for generating a swirl flow of the exhaust gas.
In a patent document 3, there is described an exhaust gas purification apparatus for an internal combustion engine which is provided with a catalyst carrier disposed in an exhaust passage of the internal combustion engine, an addition valve adapted to supply fuel into the exhaust passage at a location upstream of the catalyst carrier, and a glow plug adapted to ignite the fuel supplied from the addition valve.